DouKaku?

use strict;
use warnings;
use Btrees;
use YAML::Syck;

my $nodes = shift || 8;
sub comp{ $_[0] <=> $_[1]}
my ($tree, $node);
($tree, $node) = bal_tree_add($tree, $_, \&comp) for (1..$nodes);

for (1..$nodes){
    ($tree, $node) = bal_tree_del($tree, $_, \&comp);
    print YAML::Syck::Dump($tree);
}